Fairy Slipper Orchid, Calypso bulbosa

The cold woodlands of the northern hemisphere are the dwelling place of a tiny, delicate orchid, Calypso bulbosa, aptly named after the Greek nymph. When you first see it in person you are immediately taken back by its seductive beauty and elusive stature. This diminutive plant, also known as the fairy slipper, can be found from cold temperate regions across the northern US, up through the boreal forests of Canada and Alaska, straight across the taiga of Russia, into Scandinavia, and south through the mountains of western China, Korea and northern Japan. It is nowhere truly common, and is often overlooked.

C. bulbosa, as the name indicates, grows from a single oval subterranean bulb no bigger than the average fingernail. In the winter months a single broad, lightly pleated leaf arises just above the forest floor, only to wither in the summer months during the plant’s dormancy. It regrows again in the fall, just before the snows of winter hit. The flower stalk, occasionally up to 15 cm tall, but often much shorter, begins growth once the cold of winter has abated. Depending on exposure, as well as altitude and latitude, plants are in flower from April to June. The flowers are borne singly at the apex of the flower stalk, and are accompanied by a whitish, translucent floral bract at the pinnacle of the stalk.

fairy-slipper adult plant
Adult plants of Calypso bulbuosa typically are no more than hand high.

Despite being quite small, the flowers are startlingly beautiful, though you’ll have to get on your belly to really appreciate them. Five of the flower parts are nearly identical in size and shape, two petals and three sepals, splayed out in a star-like pattern. The lip is slipper-like, similar to a lady slipper (genus Cypripedium), but more elongated with a frilled front plate with upward curling margins. At the front of the mouth of the lip are a number of hairy bristles. At the base of the lip, sometimes extending a fairly long distance beyond the lip proper (especially in v. speciosa) are two horn-like projections. Overall flower color is pink-purple. The column is held horizontal to the ground, is relatively long and has a broad hood.

The lip is striated with white and various shades of darker purple, or purple brown veins and spots. Variety americana is known for a bright yellow patch in around the area where the bristles protrude, making it perhaps the most attractive of the four known varieties. Pure white alba flowers, as well as pale “semi-alba” types are also known. Occasionally, two flowers can be found on one stalk. Seed pods develop in an upward standing position.

Calypso bulbosa flowers
A pair of Calypso bulbosa v. occidentalis growing in a coniferous forest in East Sooke Park, Vancouver Island, Canada.

There are currently four accepted varieties of C. bulbosa:

C. bulbosa v. bulbosa – a denizen of northern Eurasia from Scandinavia and extending across the boreal forest regions of Russia to the Korean Peninsula and northern Japan. This was the first variety to be described by the father of binomial nomenclature, Linnaeus, in 1753.

C. bulbosa v. speciosa – confined to the high mountains of western China, parts of inner Mongolia and central Japan (limited to high elevations of the Southern Japanese Alps; Yamanashi, Nagano, Shizuoka, and Saitama Prefectures). Somewhat of an enigma, it is not completely certain that Chinese and Japanese plants are of the same type. In China and Japan it is found in subalpine coniferous forest up to 3,200 m (~10,500’) elevation.

C. bulbosa v. americana – found across the entire boreal region of North America from the Atlantic to Pacific, as well as the mountainous regions of the western US (in Canada it is widespread in forested regions, in the US from northern Maine, Vermont, Michigan, Wisconsin, Minnesota, South Dakota (Black Hills), Montana, Idaho, Wyoming, Washington, Utah, Colorado, New Mexico, Arizona, Alaska; historically N.Y. (last seen in 1969) and New Hampshire. Known for growing into large, clumping colonies and having yellow crested lips. Largely restricted to northern white cedar (Thuja occidentalis) and balsam fir (Abies balsamea) swamps east of the Mississippi River, but occasionally found on drier sites in mixed coniferous/deciduous forest often over limestone bedrock. In Michigan it can be found in swales between old lakeside dunes in jack pine forest (Pinus banksiana) alongside Cypripedium arietinum. In the western US it is found at mid-elevation coniferous forest in the northern Rocky Mountains, and up to 3,000 m (10,000’) in Arizona, its southernmost distribution. In Canada it is found from Labrador to British Columbia, and northward to the Northwest Territories, typically in coniferous forest.

C. bulbosa v. occidentalis – confined to western North America from California to Oregon, Washington, Idaho, Montana, British Columbia, and Alaska. In the south it is found exclusively in cool, “fog-belt” coastal forests, and further north (Idaho and Montana and northward) it can be seen in moister inland mid-elevation mountains as well. It is a characteristic plant of the Pacific Northwest rain forest belt often seen near sea level, and flowering earlier than most other varieties.

Calypso bulbosa leaves flower buds
The leaves of Calypso bulbosa grow in the fall, persist through the winter months and go dormant after flowering in the spring. In this photo you can also see the flower buds have formed and they too overwinter, so care must be taken to protect these if you are growing the plant.

My first encounter with this species was in the high mountains of Colorado near Rocky Mountain National Park. I was there in the early fall and so did not see them in flower, but their distinctive leaves gave them away. Years later I saw large colonies in the mountains around Bozeman, Montana, again in the fall. It wasn’t until I finally made a trip to the Victoria, British Columbia area in May 2019 that I finally got to see v. occidentalis in flower, growing in Douglas fir (Pseudotsuga menziesii) and western red cedar forest (Thuja plicata) just above the pounding waves of the Salish Sea. It was a magical experience for me, and upon seeing them I was immediately convinced that both Calypso and fairy slipper are very apt names for this little jewel.

Calypso bulbosa, though widely distributed, is becoming increasingly rare, particularly in the southern end of its range. It is considered rare in the lower 48 states except in a handful of states, and in the northeast it is either vulnerable, endangered or extinct. Populations in Minnesota as well as the northern Rockies and Pacific coast appear secure for now, and likely Canadian populations are by and large in pretty good shape, too. In Japan plants are in danger due to climate change since populations are confined to high mountain forests that are undergoing rapid warming. Populations in Europe are considered near threatened by the IUCN (International Union for Conservation of Nature). In all regions where urbanization is occurring (for instance around Victoria, B.C.) populations are being adversely effected by development and increased human disturbance. In various places it is also subject to over collection for the horticultural trade, for example, in the Japanese Southern Alps and the Pacific Northwest of North America.

Calypso bulbosa alba flower
All varieties of Calypso bulbosa have individuals that are either true pure white “alba” flowers, or very pale ones like this “semi-alba” flower.

First and foremost, this is a plant of cool to cold forests, hence if you want to grow it, you need to keep this in mind. It likely will not endure temperatures above 26 C (80 F) for long periods of time. The main reason it lives either at high altitude or in cedar bogs at the southern end of its range is due to the cool conditions these environments provide. Another important point is that this species does not live in soil, but rather in the thin layer of humus overlaying forest soils, or moss covered humus of bog environments. Third, this orchid appears to have a dependency on mycorrhizal fungi even throughout adulthood. For all these reasons it will be a challenge to maintain in most typical garden settings, particularly in areas that experience heat spells for more than say a few days.

Another issue in growing them is their diminutive size. They can be harmed by foot traffic, either human or animal made, very easily either through mechanical damage or the compacting of the growing medium. Snails and slugs are another bane of this plant, and unless diligently controlled, will be the end of them in short order. Rodents as well need to be kept away. Mice, voles, pika, marmots, rats and the like can make an easy snack out of a Calypso in just a few bites. Likewise, moles and burrowing animals need to be controlled lest the thin roots and tiny bulbs are damaged or exposed to the air. Finally, these plants are so small that they cannot endure much competition from neighboring plants including grasses, any type of ground cover, spreading bushes, or indeed even vigorously growing mosses.

If all that weren’t enough, something like 99.9% of the plants that you might find for sale are for certain wild collected. While that may not actually be a legal issue, and in truth this species is considered globally secure for the time being, it may give you an ethical pause. In this world of online auctions and on demand next day delivery, one can easily see that all collectable plants are more at risk than ever before. Yes, this species has been produced artificially, but only by a handful of knowledgeable enthusiasts, and certainly not on a commercial scale. So, as with all terrestrial orchid sales, buyer beware.

With all that in mind, if you still desire to grow C. bulbosa, and have access to healthy plants and proper fungal symbionts (best acquired by getting humus or conifer duff from a known habitat), then you may succeed with this species. It should be grown in shady conditions, never in direct sun. The compost needs to remain moist during the growth phase extending from fall until late spring. In summer some drying is tolerated, but droughty conditions are not recommended. Never use chlorinated water or high mineral water or you will kill them quick. Keep the growing compost cool at all times, even if the air temperatures exceed the mid 20s C (above 80 F). A northern exposure is recommended rather than southern to prevent overheating.

Grow the plants in a thin layer of partially decomposed conifer duff no more than 5 cm (2”) deep over a continuously moist layer of neutral to slightly acidic inorganic material such as river sand, perlite, Turface, small size pumice or the like. The point is that you don’t want this layer to modify the conifer duff layer chemically or mechanically, say from earthworms or soil burrowing insects. Companion plants need to be completely noncompetitive or absent altogether. A layer of moss is OK as long as it doesn’t overgrow the orchids (that’s one way they are overwhelmed even in the wild), and in fact the plants will do better by themselves. If you have a native forest, or forest-like condition in the outside garden, and you live near natural populations, you may try this one in the open garden. Otherwise I recommend growing them in containers and keeping these well protected throughout the season in an outdoor shade house or the like. Refrain from using fertilizer of any kind, even at weak dilution rates.

Calypso bulbosa flowers in nature
A group of Calypso bulbosa v. occidentalis in their full glory, East Sooke Park, Vancouver Island, British Columbia, Canada.

So, there you have it: a tiny little jewel of a plant better suited to being appreciated in nature than in a garden setting. Let’s hope this lovely little orchid continues to grace the far flung woods of the north county for many years to come.

One Reply to “Fairy Slipper Orchid, Calypso bulbosa”

  1. I’m happy to see you mention that chlorinated water is a death knell to Calypsos, and that a healthy presence of it’s fungal partner is a necessity to life.
    Excellent article on a diminutive genus which is often overlooked given it is as tall as your longest finger…and hopefully stays overlooked. Extremely hard to grow, and city life is a death knell if transplanted there.
    As always,excellent articles populate your site.

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